Method for Making a Strong Aluminum Alloy

ABSTRACT

A method is used to make an aluminum alloy with excellent tensile strength, low density and excellent radiation. The method includes the steps of providing a base material, adding 0.06 wt % to 0.30 wt % of zirconium and 0.06 wt % to 0.30 wt % of vanadium to the base material, and melting the basic material with the zirconium and vanadium to provide an aluminum alloy. The base material includes 92.55 wt % to 97.38 wt % of aluminum, 0.9 wt % to 1.8 wt % of silicon, less than 0.5 wt % of iron, 0.6 wt % to 1.2 wt % of copper, 0.4 wt % to 1.1 wt % of manganese, 0.6 wt % to 1.4 wt % of magnesium, less than 0.40 wt % of chromium, less than 0.25 wt % of zinc and less than 0.20 wt % of titanium.

BACKGROUND OF INVENTION

1. Field of Invention

The present invention relates to a method for making a strong aluminumalloy and, more particularly, to a method for providing an aluminumalloy with excellent tensile strength, hardness and radiation and lowdensity.

2. Related Prior Art

Al—Si—Mg (6000 series) alloys have been used in the defense industry,automobile industry and sports industry for being light weight. Al—Si—Mgalloys however exhibit inadequate strength and need improvement.

To improve the strength of commercially available Al—Si—Mg alloys, theymay be added with Sc as a grain refiner. The concentration of the Sc isabout 0.03% to 0.20% to increase the tensile strength and hardness ofthe Al—Si—Mg alloys to about 450 MPa.

Sc is rare and therefore expensive. Accordingly, the Al—Si—Mg alloysadded with the Sc are expensive.

The present invention is therefore intended to obviate or at leastalleviate the problems encountered in conventional alloy.

SUMMARY OF INVENTION

It is the primary objective of the present invention to provide a methodfor making an aluminum alloy with excellent tensile strength, lowdensity and excellent radiation.

To achieve the foregoing objective, the method includes the steps ofproviding a base material, adding 0.06 wt % to 0.30 wt % of zirconiumand 0.06 wt % to 0.30 wt % of vanadium to the base material, and meltingthe basic material with the zirconium and vanadium to provide analuminum alloy.

The base material includes 92.55 wt % to 97.38 wt % of aluminum, 0.9 wt% to 1.8 wt % of silicon, less than 0.5 wt % of iron, 0.6 wt % to 1.2 wt% of copper, 0.4 wt % to 1.1 wt % of manganese, 0.6 wt % to 1.4 wt % ofmagnesium, less than 0.40 wt % of chromium, less than 0.25 wt % of zincand less than 0.20 wt % of titanium.

In another aspect, the step of melting the base material with thezirconium and vanadium includes the step of providing an inductionfurnace for melting the base material with the zirconium and vanadium inargon.

In another aspect, the method further includes the steps of degassingand slag-removing the aluminum alloy melt, turning the aluminum alloymelt into an aluminum alloy nugget by direct chill casting, andpressurizing the aluminum alloy nugget to turn the aluminum alloy nuggetinto another shape.

In another aspect, the step of pressurizing the aluminum alloy nuggetincludes the step of extruding the aluminum alloy nugget. The step ofextruding the aluminum alloy nugget may include the step of providing anextruding machine.

In another aspect, the step of pressurizing the aluminum alloy nuggetincludes the step of providing a rolling machine for rolling thealuminum alloy nugget. The step of rolling the aluminum alloy nugget mayinclude the step of providing a rolling machine.

Other objectives, advantages and features of the present invention willbe apparent from the following description referring to the attacheddrawings.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will be described via detailed illustration of thepreferred embodiment referring to the drawings wherein:

FIG. 1 is a flow chart of a method for providing an aluminum alloy withexcellent tensile strength, hardness and radiation and low densityaccording to the preferred embodiment of the present invention;

FIG. 2 is a table of compositions of alloys made by the method shown inFIG. 1 and a conventional alloy;

FIG. 3 is a table of several mechanical properties of the alloys shownin FIG. 2 after extruding; and

FIG. 4 is a table of several mechanical properties of the alloys shownin FIG. 2 after T6 heat treatment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Referring to FIG. 1, there is shown a method for providing an aluminumalloy with excellent mechanical properties. The excellent mechanicalproperties include tensile strength, hardness and radiation and lowdensity.

At first, there is provided a base material 10. The base material 10includes 92.55 wt % to 97.38 wt % of aluminum 101, 0.9 wt % to 1.8 wt %of silicon 102, 0.5 wt % of iron 103, 0.6 wt % to 1.2 wt % of copper104, 0.4 wt % to 1.1 wt % of manganese 105, 0.6 wt % to 1.4 wt % ofmagnesium 106, less than 0.4 wt % of chromium 107, less than 0.25 wt %of zinc 108 and less than 0.20 wt % of titanium 109. Then, the basicmaterial 10 is added with zirconium 111 and vanadium 112, and molten inargon in an induction furnace, thus providing aluminum alloy melt 11.

Secondly, the aluminum alloy melt 11 is subjected to degassing andslag-removing before it is subjected to extruding b in the form of chillcasting to provide an aluminum alloy nugget 12.

Thirdly, the aluminum alloy nugget 12 is subjected to pressurizing c,thus providing an aluminum alloy product 1. The aluminum alloy nugget 12is made into the aluminum alloy product 1 by extruding or rolling. Forexample, the aluminum alloy nugget 12 may be made into the aluminumalloy product 1 in the form of a rod or plank with an extruding machine.Alternatively, the aluminum alloy nugget 12 may be made into thealuminum alloy product 1 in the form of a board or sheet with a rollingmachine.

Referring to FIG. 2, aluminum 101, silicon 102, magnesium 106, copper104, manganese 105, zirconium 111 and scandium may be used to provide afirst specimen. Aluminum 101, silicon 102, magnesium 106, copper 104,manganese 105, zirconium 111 and vanadium 112 may be used to providesecond and third specimens. Aluminum 101, silicon 102, magnesium 106,copper 104 and manganese 105 may be used to provide a conventionalalloy.

Referring to FIGS. 3 and 4, the first specimen, which is added withscandium, is made with a tensile strength of 240 MPa and a percentageelongation of 19.4%. The second and third specimens, which are addedwith zirconium 111 and vanadium 112, are respectively made with tensilestrengths of 212 MPa and 225 MPa and percentage elongations of 18.5% and17.9%.

After T6 heat treatment, the tensile strength of the first specimen,which is added with scandium, is increased to 478 MPa, and thepercentage elongation is reduced to 11.5%. The fourth specimen, which isadded with zirconium 111 and vanadium 112, is made with a tensilestrength of 202 MPa and a percentage elongation of 19.5%. After the T6heat treatment, the tensile strengths of the second and third specimens,which are added with zirconium 111 and vanadium 112, are respectivelyincreased to 455 MPa and 475 MPa, and the percentage elongations arereduced to 13.1% and 12.5%. It is learned that the tensile strengths ofthe alloys 1 and 3 are similar to one another after the T6 treatment.The second specimen exhibits the best percentage elongation. The secondspecimen exhibits a lower tensile strength than the first and thirdspecimens for including less manganese 105, a strength phase. After theT6 heat treatment, the tensile strength of the fourth specimen, which isadded with zirconium 111 and vanadium 112, is increased to 400 MPa, andthe percentage elongation is reduced to 14.7%.

The grain-refining of aluminum alloys is mainly done by addition ofgrain refiners such as scandium (“Sc”) and zirconium 111 (“Zr”) to growprecipitates such as Al₃Sc at grain boundaries to interfere with thegrowth of the grains. Alternatively, a strengthening phase may bedistributed in the grains. When the grains are refined and strengthened,the grain boundaries are effective obstacles against slip, concentrationof stress in front of the grain boundaries activate a lot of slipsystems, and deformation of the alloys become even. Thus, the strengthand tenacity of the alloys are increased. The relation of the yieldstrengths of the alloys to the sizes of the grains can be expressed in aHall-Petch equation, i.e., σ_(yield)=σ₀+kd^(−1/2), wherein σ₀ stands forthe yield strength of a single grain, k stands for a slope in theHall-Petch equation, and d stands for the size of the grain.

The T6 heat treatment of Al alloy is a well-known technique of the 6000series, which is the artificial aging after the solution treatment. Inthe solution treatment, the material is heated above the solution lineto become a single solution phase; and, then, is quenched at a hightemperature. Thus, the single solution phase is quickly cooled down toget an oversaturated solution. In the artificial aging, theoversaturated solution is put in a furnace with a certain temperaturekept for gradually precipitating precipitate with changedcharacteristics. For example, in one preferred embodiment, the heattreatment of Al alloy in the present invention is as follows: a solutiontreatment at 530° C. with the temperature kept for 1 hour; a quenchingat 25° C., which is a water quenching; and an artificial aging at 177°C. with the temperature kept for 8 hours.

Based on the 6066-T6 alloy, the present invention preferably adds smallamounts of V and Zr with a ratio of Si/Mg between 1.2 and 1.5 to form astrengthening phase of Mg₅Si₄. In a preferred embodiment, the T6 of thepresent invention has a tensile strength of 475 MPa and a yield strengthof 417 MPa, which is better than the tensile strength of the prior art.

Applicant notes that the recited prior art typically includes expensiverare earth elements, while Applicant's recited composition preferablyavoids the costly rare earth elements. Applicant further notes that therecited invention is based on 6066-T6 alloy melted with a particularamount of V and Zr. In one preferred embodiment, the anti-stretchingstrength of the alloy after T6 is 475 MPa, the yield strength is 417 MPaand the extensibility is 12.5%. All these are clearly better than thoseof conventional 6066-T6, which are 395 MPa of anti-stretching strength,359 MPa of yield strength and 12% of extensibility. In addition, themechanical characteristics exceed those of the mechanicalcharacteristics of the conventional 6066-T6 alloy modified with additionof expensive Sc in alloy. Thus, the recited invention not only hasbetter mechanical characteristics than traditional 6066 alloy, but alsohas a reduced cost of alloy.

Further, the present invention improves the mechanical strength of theAl—Si—Mg alloy for broadening the application fields of the device.Without adding the rare earth metal Sc, the present invention adds smallamounts of Zr and V as grain refiners to strengthen the tensility of thealloy to, in a preferred embodiment, about 450 MPa or, in anotherpreferred embodiment, 400 MPa.

The method of the present invention provides aluminum alloys without thedrawbacks of the prior art. For example, the aluminum alloys of thepresent invention exhibit high tensile strengths, excellent plasticdeformations, low densities, radiations and hardness. Hence, thealuminum alloys of the present invention can be used in shells in thedefense industry, the aerospace industry, the automobile industry, theappliance industry and the OA industry for example.

The present invention has been described via the detailed illustrationof the preferred embodiment. Those skilled in the art can derivevariations from the preferred embodiment without departing from thescope of the present invention. Therefore, the preferred embodimentshall not limit the scope of the present invention defined in theclaims.

1. A method for making a strong aluminum alloy including the steps ofproviding a base material consisting essentially of 92.55% to 97.38% ofaluminum, 0.9% to 1.8% of silicon, less than 0.5% of iron, 0.6% to 1.2%of copper, 0.4% to 1.1% of manganese, 0.6% to 1.4% of magnesium, lessthan 0.40% of chromium, less than 0.25% of zinc and less than 0.20% oftitanium; adding 0.06% to 0.16% of zirconium and 0.06% to 0.30% ofvanadium to the base material, the above all percentages being byweight, and melting the basic material with the zirconium and vanadiumto provide an aluminum alloy having a strength of 400 Mpa after a T6heat treatment.
 2. The method for making a strong aluminum alloyaccording to claim 1, wherein the step of melting the base material withthe zirconium and vanadium includes the step of providing an inductionfurnace for melting the base material with the zirconium and vanadium inargon to provide an aluminum alloy melt.
 3. The method for making astrong aluminum alloy according to claim 2, further including the stepsof subjecting the aluminum alloy melt to degassing and slag-removing;turning the aluminum alloy melt into an aluminum alloy nugget by directchill casting; and pressurizing the aluminum alloy nugget to turn thealuminum alloy nugget into another shape.
 4. The method for making astrong aluminum alloy according to claim 3, wherein the step ofpressurizing the aluminum alloy nugget includes the step of extrudingthe aluminum alloy nugget.
 5. The method for making a strong aluminumalloy according to claim 4, wherein the step of extruding the aluminumalloy nugget includes the step of providing an extruding machine.
 6. Themethod for making a strong aluminum alloy according to claim 3, whereinthe step of pressurizing the aluminum alloy nugget includes the step ofproviding a rolling machine for rolling the aluminum alloy nugget. 7.The method for making a strong aluminum alloy according to claim 6,wherein the step of rolling the aluminum alloy nugget includes the stepof providing a rolling machine.